Valve systems in aircraft fuel systems typically comprise a valve located within a fuel tank, fuel line, or other enclosed environment, the valve being arranged to be moved by an actuator. For example, the valve may be in the form of a ball-valve arranged to be rotated between its shut and open positions via a shaft actuated by the actuator.
In a known valve system, the valve is positioned within an aircraft fuel tank and the actuator is located outside of the fuel tank for safety reasons, the actuator thus being positioned remotely from the valve, ensuring that the electrical equipment associated with the actuator is kept remote from and out of contact with fuel in the fuel tank. The position of the valve is determined by measuring the position of the actuator.